Olefin polymerization catalysts are of great use in industry. Hence there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on substituted metallocenes as catalyst precursors, which are activated either with the help of an alumoxane, or with an activator containing a non-coordinating anion.
For example, U.S. Pat. No. 7,829,495 discloses Me2Si(fluorenyl)(3-nPr-Cp)ZrCl2 and U.S. Pat. No. 7,179,876 discloses supported (nPrCp)2HfMe2.
Further, Stadelhofer, J.; Weidlein, J.; and Haaland, A., J. Organomet. Chem., 1975, 84, C1-C4 discloses preparation of potassium cyclopentadienide.
Additionally, Me2C(Cp)(Me3SiCH2-Ind)MCl2 and Me2C(Cp)(Me,Me3SiCH2-Ind)MCl2, where M is Zr or Hf have been synthesized and screened for the syndiospecific polymerization of propylene, see Leino, R.; Gomez, F.; Cole, A.; and Waymouth, R., Macromolecules, 2001, 34, pp. 2072-2082.
Background references include U.S. Publication No. 2009/0297810, WO 2016/171807, WO 2016/094,843, WO 2016/172,099, and JP 5 262405B.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, or to alter comonomer distribution without deteriorating the resulting polymer's properties. There is especially a need to produce linear low density polyethylene where the comonomer used to disrupt the ethylene run lengths to reduce crystallinity is efficient. The catalyst systems described herein are particularly efficient at yielding linear low density polyethylene with efficient use of comonomer.
It is therefore an object of the present invention to provide novel catalyst compounds, catalysts systems comprising such compounds, and processes for the polymerization of olefins using such compounds and systems.